Qt. Copying file error while trying to run the project. How to fix a mistake and why is it happening?

Question

I’m trying to install and create the first Qt project. I am using CLion with CMake and Qt 6. I set up CMake:

cmake_minimum_required(VERSION 3.17)
project(QSnake)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_AUTOUIC ON)

set(QT_VERSION 6)
set(REQUIRED_LIBS Core Gui Widgets)
set(REQUIRED_LIBS_QUALIFIED Qt6::Core Qt6::Gui Qt6::Widgets)

set(CMAKE_PREFIX_PATH D:/Qt/6.0.2/mingw81_64/lib/cmake)

add_executable(${PROJECT_NAME} main.cpp)

if(NOT CMAKE_PREFIX_PATH)
    message(WARNING "CMAKE_PREFIX_PATH is not defined, you may need to set it "
                    "(-DCMAKE_PREFIX_PATH=\"path/to/Qt/lib/cmake\" or -DCMAKE_PREFIX_PATH=/usr/include/{host}/qt{version}/ on Ubuntu)")
endif()
find_package(Qt${QT_VERSION} COMPONENTS ${REQUIRED_LIBS} REQUIRED)
target_link_libraries(${PROJECT_NAME} ${REQUIRED_LIBS_QUALIFIED})
if(WIN32)
    set(DEBUG_SUFFIX)
    if (CMAKE_BUILD_TYPE MATCHES "Debug")
        set(DEBUG_SUFFIX "d")
    endif()
    set(QT_INSTALL_PATH "${CMAKE_PREFIX_PATH}")
    if(NOT EXISTS "${QT_INSTALL_PATH}/bin")
        set(QT_INSTALL_PATH "${QT_INSTALL_PATH}/..")
        if(NOT EXISTS "${QT_INSTALL_PATH}/bin")
            set(QT_INSTALL_PATH "${QT_INSTALL_PATH}/..")
        endif()
    endif()
    if(EXISTS "${QT_INSTALL_PATH}/plugins/platforms/qwindows${DEBUG_SUFFIX}.dll")
        add_custom_command(TARGET ${PROJECT_NAME} POST_BUILD
                COMMAND ${CMAKE_COMMAND} -E make_directory
                "$<TARGET_FILE_DIR:${PROJECT_NAME}>/plugins/platforms/")
        add_custom_command(TARGET ${PROJECT_NAME} POST_BUILD
                COMMAND ${CMAKE_COMMAND} -E copy
                "${QT_INSTALL_PATH}/plugins/platforms/qwindows${DEBUG_SUFFIX}.dll"
                "$<TARGET_FILE_DIR:${PROJECT_NAME}>/plugins/platforms/")
    endif()
    foreach(QT_LIB ${REQUIRED_LIBS})
        add_custom_command(TARGET ${PROJECT_NAME} POST_BUILD
                COMMAND ${CMAKE_COMMAND} -E copy
                "${QT_INSTALL_PATH}/bin/Qt${QT_VERSION}${QT_LIB}${DEBUG_SUFFIX}.dll"
                "$<TARGET_FILE_DIR:${PROJECT_NAME}>")
    endforeach(QT_LIB)
endif()

Actually, this is how it was generated when the CLion project was created. I only set the path: D:/Qt/6.0.2/mingw81_64/lib/cmake

Just in case, I will also add the main.c code. It is also generated by CLion.

#include <QApplication>
#include <QPushButton>

int
main(int argc,
     char *argv[])
{
    QApplication a(argc, argv);
    QPushButton button("Hello world!", nullptr);
    button.resize(200, 100);
    button.show();
    return QApplication::exec();
}

I don’t see any problems with CMake, but when I try to run the project there is an error:

Error copying file "D:/Qt/6.0.2/mingw81_64/lib/cmake/../../bin/Qt6Cored.dll" to "D:/QSnake/cmake-build-debug".
mingw32-make[3]: *** [CMakeFiles\QSnake.dir\build.make:126: QSnake.exe] Error 1
mingw32-make[3]: *** Deleting file 'QSnake.exe'
mingw32-make[2]: *** [CMakeFiles\Makefile2:96: CMakeFiles/QSnake.dir/all] Error 2
mingw32-make[1]: *** [CMakeFiles\Makefile2:103: CMakeFiles/QSnake.dir/rule] Error 2
mingw32-make: *** [Makefile:137: QSnake] Error 2

What is this error and how do I fix it? I understand that there is no problem with build - only a copying error. And should copied dll be called "Cored" and not "Core"?

Thank you for your attention! If you need any additional information, please let me know - I will try to clarify the question.

score 4 · Accepted Answer · answered Mar 17 '21 at 20:59

4

Problem solved. Whether it is useful to anyone, but the CMake automatically generated by CLion contains rows that cause an error in debug mode (adds 'd' suffix to all dll files):

if (CMAKE_BUILD_TYPE MATCHES "Debug")
    set(DEBUG_SUFFIX "d")
endif()

Deleting those lines saved me :)

answered Mar 17 '21 at 20:59

lrdfthflies

85
8

3

This only masks the problem. You didn’t instal the debug build of Qt. The installer has an option for that. – Kuba hasn't forgotten Monica Mar 17 '21 at 21:59
I deleted it, now it says "Entry point into procedure is not found" – GaussGun Oct 12 '22 at 13:59
@Kubahasn'tforgottenMonica please tell me what option I should install (for Qt 5.12.2). I installed everything that includes "debug" in it except for Qt Creator related, and this still doesn't work! – GaussGun Oct 12 '22 at 14:43

score 1 · Answer 2 · answered Dec 23 '21 at 03:19

1

The real answer to this is that you are using a CMake profile defined as "debug", while you have not installed a debug version of Qt.

To solve, and not patch, if you don't want to download the debug DLLs, then create a CMake profile for "release".

answered Dec 23 '21 at 03:19

Luc Morin

5,302
20
39

score 0 · Answer 3 · answered Apr 10 '22 at 11:39

I had the same problem and none of the answers here solved the problem. Here is how I could solved it for myself:

TL;DR:

set prefix-path when creating project
copy missing Qt6Cored.dll into bin-folder

When creating the new project in Clion be sure to set the correct prefix-path:

You can see in your error message that /bin/Qt6Cored.dll gets added to the prefix path automatically, so you don't have to select the bin folder when setting the prefix-path.

After this I still got an error message (but path was displayed correctly without any "/../..").

I then realized that there was no Qt6Cored.dll in my bin-folder:

So I simply copied the missing file from C:\Qt\6.1.3\msvc2019_64\bin into C:\Qt\6.1.3\mingw81_64\bin

And then it worked!

If you don't have the msvc2019_64 folder you can install it by modifying Qt via app-settings:

Qt. Copying file error while trying to run the project. How to fix a mistake and why is it happening?

3 Answers3